In a combustion chamber, such as a combustion chamber of a gas turbine, a mixture of fuel and compressed air is burned. Thereby, the compressed air and the fuel is supplied to the combustion chamber and the combustion product is expelled from the combustion chamber resulting in a flow of material. Due to the supply of fuel and compressed gas and due to the exhaustion of the combustion product pressure oscillations evolve within the combustion chamber which may be characterized by a pressure oscillation frequency. The pressure oscillation frequency may in particular depend on a mass and/or flow velocity of the supplied fuel and supplied compressed air as well as on the mass and/or flow velocity of the expelled combustion product and may also depend on the geometry of the combustion chamber. Typical pressure oscillation frequencies may be in the range between 50 Hz and 1500 Hz, in particular around about 100 Hz.
These pressure oscillations adversely affect the operation of the combustion chamber, in particular the efficiency of the gas turbine comprising the combustion chamber. For damping the pressure oscillations within a combustion chamber it is known to attach a so-called Helmholtz resonator at the combustion chamber, such that an inside of the Helmholtz resonator is in communication with the combustion space defined by the combustion chamber.
From DE 10 2005 052 881 A1 a heating device including a combustion chamber is known, wherein the combustion chamber is connected to a flow channel which is coupled to a Helmholtz resonator for damping pressure oscillations. The temperature of the gas contained within the Helmholtz resonator may be changed to adapt a working frequency of the Helmholtz resonator to the oscillation within the combustion chamber.
EP 0 974 788 A1 discloses a Helmholtz resonator with a nozzle arrangement for generating a mixture of air and liquid before entry in a flow channel for damping oscillations within the flow channel.
GB 2,288,660 A discloses an apparatus for damping thermoacoustic vibrations in a combustion chamber of a gas turbine, wherein a Helmholtz resonator is connected to a combustion chamber for damping the combustion chamber oscillations. This document also discloses a control system which controls a heating element for heating the gas within the Helmholtz resonator based on a phase difference of two pressures measured within the combustion chamber and the Helmholtz resonator, respectively.
It has been observed that a combustion chamber may not work satisfactorily under changing running conditions. There may be a need for a resonator device which is suitable for damping a pressure oscillation within a combustion chamber which is in particular adaptable for different running conditions of the combustion chamber. In particular, there may be a need for a resonator device which is suitable for damping pressure oscillations of different frequencies which rapidly change in time and there may be a need for a method of operating a combustion arrangement at different running conditions.